perf: conversational fast-path (skip enrichment) + shorter silence wait

Greetings/small-talk routed no data tool yet still ran the episodic memory
enrichment (LLM keyword extract + diary/graph search, ~1s) every turn. Skip it
when the router picked no external-data tool — the always-injected warm profile
still personalises the reply. Also drop the voice silence-detection wait
800ms -> 600ms for snappier turn-taking. Warm "안녕" now lands well under the
3-4s target.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

docker-compose.yml

@@ -77,6 +77,7 @@ services:
       PLANNER_ENABLED: ${PLANNER_ENABLED:-0}
       # Lock STT to Korean (skip Whisper auto-detect).
       STT_LANGUAGE: ${STT_LANGUAGE:-ko}
+      VOICE_SILENCE_MS: ${VOICE_SILENCE_MS:-600}
       BRIDGE_URL: http://127.0.0.1:8765
     depends_on:
       - ollama